The commemorative stone column conceals a secret laboratory.

The Great Fire of London and the regulation of one-way streets both started in this alley.

During World War II, this rice mill became a Nazi concentration camp.

The Adriatic's most famous wind can be reliably experienced in the city's Marina.

A cone-shaped top and cylindrical body set this 900-year-old structure apart from other Italian bell towers.

A star-shaped fortress town fort built in the geometric model of the Renaissance utopian city.

See how paper is made the old-fashioned way.

This stone figurine was made more than 6,000 years ago and depicts a female deity of the Neolithic Vinča culture.

A neighborhood church's unusual abstract stained glass was the final project of avant-garde artist Jean Cocteau.

An extensive collection of reliquaries containing the bones of saints housed in the largest Catholic church in Venice.

Despite a fraught and controversial history this African island holds a powerful monument to the tragedy of the slave trade.

This tiny, tranquil Senegalese island serves as a powerful symbol of the Atlantic slave trade.

An ancient Egyptian temple in the middle of Madrid, Spain.

The remains of a convent turned military barrack in the heart of Madrid.

Just like in Hollywood, Madrid has also a forgotten walk of fame.

A curious memento mori hangs in the magnificent Cathedral of Segovia.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

These "mermaids" that surround a plaza in Segovia are rather sphinx-like.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

This influential Renaissance-era library was once the haunt of kings and monks.

This 18th-century project to build the world's tallest gravity dam was never completed.

An ode to the famous Las Vegas signage.

These Bullet-scarred bunkers are haunting reminders of the Spanish Civil War.

This airport currywurst stand is made out of retro airplane parts.